1. Field of the Invention
The present invention relates to a motor apparatus.
2. Description of Related Art
In general, a wiper motor apparatus, such as a rear wiper motor apparatus (or simply referred to as a rear wiper motor), has a gear housing, which receives a speed reducing mechanism and a swing mechanism. The swing mechanism converts rotational movement of the motor into reciprocal swing movement to reciprocally rotate an output shaft of the motor.
An example of a rear wiper motor includes a rear wiper motor 200 of FIG. 20 that has a swing mechanism 208. One such wiper motor having the swing mechanism is disclosed in, for example, Japanese Patent No. 3550049. The swing mechanism 208 of FIG. 20 has a reciprocally swingable sector gear 206, which is meshed with a gear 204 that rotates integrally with an output shaft 202 (the gear 204 possibly rotating integrally with the output shaft 202 through a transmission member, such as a clutch), to reciprocally rotate the output shaft 202 through a large angular range (a wide angular range). Also, as shown in FIG. 21, there has been proposed a rear wiper motor 250 that serves as a rear wiper motor of a wide angular range type and includes a swing mechanism 258, in which a reciprocally movable rack 256 is meshed with a gear 254 that is rotated integrally with an output shaft 252.
Furthermore, as shown in FIG. 22, there has been proposed a rear wiper motor 300 that includes a swing mechanism 308, which includes a reciprocally swingable rod 306 connected to a lever 304 that rotates integrally with an output shaft 302. The swing mechanism 308 reciprocally rotates the output shaft 302 through a narrow angular range (not exceeding 180 degrees, and a maximum of 120 degrees). One such rear wiper motor having the swing mechanism of the narrow angular range type is disclosed in, for example, Japanese Patent No. 3180018. The rear wiper motor 300 of the narrow angular range type has a simple structure and can be manufactured at low costs.
In the rear wiper motor of the wide angular range type and the rear wiper motor of the narrow angular range type, some components, such as the output shaft and the wheel gear rotated by the motor main body or the drive force of the motor main body, are basically common to both of these rear wiper motors. However, the swing mechanism, which is located between the wheel gear and the output shaft, differs between the rear wiper motor of the wide angular range type and the rear wiper motor of the narrow angular range type. Specifically, as shown in FIG. 22, in the swing mechanism 308 of the narrow angular range type, one end of the lever 304 is secured to a base end of the output shaft 302, and the other end of the lever 304 is connected to the rod 306, which is, in turn, connected to the wheel gear 310 at an eccentric point. In contrast, as shown in FIG. 20, in the case of the swing mechanism 208 of the wide angular range type, the gear 204 is secured to a base end of the output shaft 202. The gear 204 is meshed with the gear teeth of the sector gear 206, which is connected to the eccentric point of the wheel gear 210. Even in the case of the swing mechanism 258 of the wide angular range type of FIG. 21, the gear 254, which is secured to the output shaft 252, is meshed with the gear teeth of the rack 256 that is connected to the eccentric point of the wheel gear 260. Thus, it is difficult to form the swing mechanism as a common component, which can be commonly used for both of the rear wiper motor of the wide angular range type and the rear wiper motor of the narrow angular range type. As a result, it has been required to manufacture the swing mechanisms for the respective motors of different types.
Particularly, in the case of the rear wiper motor, which has a clutch device installed to an output shaft to protect a swing mechanism and a speed reducing mechanism from an excessively large external force, it is desirable to handle the clutch device as a single component by installing the clutch device to the output shaft. However, in the case where the structure of the swing mechanism of the wide angular range type is different from the structure of the swing mechanism of the narrow angular range type, the components installed to the output shaft are different between these two types. Thus, different output shaft assemblies, which correspond to the different types, need to be formed, and therefore the manufacturing costs could be increased.